Parameter configuration and inertia power matching method for parallel systems of grid-connected converters

Abstract

This invention discloses a method for parameter configuration and inertia power matching in a parallel system of grid-connected and grid-connected converters. The parameter configuration method includes: obtaining the power frequency response transfer functions of the grid-connected and grid-connected converters based on a small-signal model of the power frequency response of the parallel system; constructing a consistency between the power frequency response transfer functions of the grid-connected and grid-connected converters to obtain a constructor function; and configuring the parameters of the phase-locked loop (PLL) of the grid-connected converter according to the constructor function. This invention solves the problem in the prior art where the power frequency responses of the grid-connected and grid-connected converters are inconsistent, making it difficult to match the inertia power in a parallel system of grid-connected and grid-connected converters.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of converter control, and particularly relates to a grid-forming / grid-following converter parallel system parameter configuration and inertia power matching method. BACKGROUND

[0002] With the large-scale application of grid-forming converters (GFM) and grid-following converters (GFL) in new power systems, the "low inertia" problem of new power systems is becoming more and more serious. In order to improve the inertia level of the system, grid-forming virtual synchronous machine (VSG) control and grid-following virtual inertia control technology are currently common solutions.

[0003] For a GFM using a VSG control strategy, self-synchronization is achieved through an active synchronous loop, while a GFL achieves phase synchronization through a phase-locked loop (PLL). The difference in synchronization methods leads to a large difference in frequency response of the two types of converters in the parallel system, which in turn makes it difficult to match the inertia power response.

[0004] At present, there has been some research on the distribution of steady-state power, but the distribution of power at the moment of disturbance still needs to be solved. In addition, the existing virtual inertia control strategy requires additional filtering links, which further exacerbates the difficulty of matching the inertia power of the parallel system. However, for a parallel system, when the equivalent inertia of each power electronic equipment is matched, the system can achieve the best power distribution and optimal frequency response performance.

[0005] Based on the above analysis, how to achieve matching control of the inertia power of the parallel system is a difficult problem that needs to be solved. SUMMARY

[0006] To solve the problems in the prior art, the present application provides a grid-forming / grid-following converter parallel system parameter configuration and inertia power matching method to solve the problem that the power frequency response of the grid-forming converter and the grid-following converter is inconsistent in the prior art, thereby making it difficult to match the inertia power of the grid-forming / grid-following converter parallel system.

[0007] To achieve the above purpose, the technical solution adopted by the present application is as follows:

[0008] In a first aspect, a grid-forming / grid-following converter parallel system parameter configuration method is provided, comprising: based on a power frequency response small signal model of a grid-forming / grid-following converter parallel system, obtaining a power frequency response transfer function of a grid-forming converter and a power frequency response transfer function of a grid-following converter; constructing the power frequency response transfer function of the grid-forming converter and the power frequency response transfer function of the grid-following converter to be consistent to obtain a construction function; and configuring parameters of a phase-locked loop of the grid-following converter according to the construction function; wherein the phase-locked loop filter of the grid-following converter is a first-order inertia link, and the loop filter transfer function is:

[0009] ;

[0010] wherein G LP (s) is a first-order inertial element of the phase-locked loop filter, s is a differential operator, k p is a proportional coefficient, k i is an integral coefficient; under the premise that the distribution coefficient K of the grid-following converter is n+1, the construction functions of k p and k i are as follows:

[0011] ;

[0012] wherein, n is the capacity ratio of the grid-constructing converter to the grid-following converter, is the rated angular frequency of the grid, is the virtual inertia coefficient of the grid-constructing converter, is the damping coefficient of the grid-constructing converter, U pu is the voltage unit value, is the synchronization coefficient.

[0013] Further, in an ideal state, the power frequency response transfer function of the grid-constructing converter is as follows:

[0014] ;

[0015] wherein a i is the numerator coefficient of the transfer function, b i is the denominator coefficient of the transfer function, i=1,2,...n, is the output angular frequency of the grid-constructing converter, is the virtual inertia coefficient of the grid-following converter, is the damping coefficient of the grid-following converter, is the active power of the load, m is the line impedance synchronization coefficient, and the superscript “ ” represents a small perturbation.

[0016] Further, in an ideal state, the power frequency response transfer function of the grid-following converter is as follows:

[0017] ;

[0018] wherein, is the output angular frequency of the grid-following converter.

[0019] Furthermore, the power frequency response transfer function of the grid-type converter and the grid-connected converter are constructed to be consistent, including: adding a distribution coefficient K before the grid-connected converter to ensure that power is distributed according to capacity during disturbances; thereby, the power frequency response transfer function of the grid-type converter is adjusted to be...

[0020] ;

[0021] The power frequency response transfer function of the grid-connected converter is adjusted to...

[0022] .

[0023] Furthermore, to ensure consistency between the power frequency response transfer function of the grid-type converter and the power frequency response transfer function of the wire-type converter, the method also includes: making This ensures that the power frequency response transfer function of the adjusted grid converter is consistent in form with that of the ground grid converter.

[0024] Furthermore, to ensure consistency between the power frequency response transfer function of the grid-type converter and the power frequency response transfer function of the ground-mounted converter, the method also includes: ensuring the active power reference value P... ref The response is adjusted to a step signal;

[0025] Load power P load To the active power reference value P ref The transfer function is,

[0026] ;

[0027] At the same time, Therefore, the virtual inertia parameter and the primary frequency modulation parameter satisfy: .

[0028] In a second aspect, a parameter configuration system for a grid-connected converter parallel system is provided, comprising a storage medium and a processor; the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the parameter configuration method for the grid-connected converter parallel system described in the first aspect.

[0029] Thirdly, a method for inertia power matching in a parallel system of grid-connected converters is provided. The method for configuring parameters of a parallel system of grid-connected converters described in the first aspect is used to configure phase-locked loop parameters of the grid-connected converters to ensure consistent power and frequency response. This method enables the power of the parallel system of grid-connected converters to be distributed according to capacity during disturbances, i.e., inertia power matching.

[0030] Fourthly, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the parameter configuration method for a grid-connected converter parallel system as described in the first aspect.

[0031] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention obtains the power frequency response transfer functions of the grid-type converter and the grid-connected converter based on the small-signal model of the power frequency response of the parallel system of grid-type and grid-connected converters; configures the phase-locked loop parameters according to the power frequency response transfer functions of the grid-type and grid-connected converters; and achieves the consistency of the power frequency response of the grid-type and grid-connected converters, thereby realizing the matching control of the inertia power of the parallel system of grid-type and grid-connected converters. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the main process of a parameter configuration method for a grid-connected converter parallel system provided by an embodiment of the present invention;

[0033] Figure 2 This is the small-signal model of the power frequency response of the parallel system of grid-connected converters in this embodiment of the invention;

[0034] Figure 3 This is the adjusted small-signal power frequency response model of the parallel system of grid-connected converters in this embodiment of the invention;

[0035] Figure 4 The above is a Bode plot of the power frequency response of a grid-connected converter parallel system under ideal conditions in an embodiment of the present invention, wherein (a) is the amplitude gain of GFM and GFL using the parameter configuration method described in the present invention, (b) is the amplitude gain of GFM and GFL without using the parameter configuration method described in the present invention, (c) is the phase gain of GFM and GFL using the parameter configuration method described in the present invention, and (d) is the phase gain of GFM and GFL without using the parameter configuration method described in the present invention.

[0036] Figure 5 The above are Bode diagrams of the power frequency response of the grid-connected converter parallel system under non-ideal conditions in the embodiments of the present invention, wherein (a) is the amplitude gain of GFM and GFL using the parameter configuration method of the present invention, (b) is the amplitude gain of GFM and GFL without using the parameter configuration method of the present invention, (c) is the phase gain of GFM and GFL using the parameter configuration method of the present invention, and (d) is the phase gain of GFM and GFL without using the parameter configuration method of the present invention.

[0037] Figure 6The simulation waveforms of the phase-locked loop without using the parameter configuration method of the parallel system of grid-connected converters described in this invention are as follows: (a) is the power response simulation waveform, and (b) is the frequency response simulation waveform.

[0038] Figure 7 The simulation waveforms are phase-locked loop waveforms using the parameter configuration method for parallel systems of grid-connected converters described in this invention, where (a) is the power response simulation waveform and (b) is the frequency response simulation waveform. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0040] Example 1

[0041] like Figures 1-7 As shown, a parameter configuration method for a parallel system of grid-connected converters includes: obtaining the power frequency response transfer function of the grid-connected converter and the power frequency response transfer function of the grid-connected converter based on the small-signal model of the power frequency response of the parallel system of grid-connected converters; performing consistency construction on the power frequency response transfer function of the grid-connected converter and the power frequency response transfer function of the grid-connected converter to obtain the constructor function; and configuring the parameters of the phase-locked loop of the grid-connected converter according to the constructor function.

[0042] Based on the small-signal model of the power frequency response of parallel systems of grid-connected and grid-connected converters, the power frequency response transfer functions of the grid-connected and grid-connected converters are obtained. Figure 1 For the small-signal model of the power frequency response of a grid-connected converter system, the loop filter of its phase-locked loop is a first-order inertial element, i.e.:

[0043]

[0044] Among them, G LP (s) is the first-order inertial element of the phase-locked loop filter, s is the differential operator, and k p k is the proportionality coefficient. i is the integral coefficient.

[0045] According to the small-signal model of the power frequency response of a grid-connected converter system, the power frequency response transfer function of the grid-connected converter is:

[0046]

[0047] Among them, a i For the numerator coefficient of the transfer function, b iThe coefficients in the denominator of the transfer function are i=1,2,...n, where n is the capacity ratio of the grid-type converter to the grid-connected converter, and T is the transfer function coefficient. f The filtering time constant is For the output angular frequency of the grid-type converter, The rated angular frequency of the power grid. The virtual inertia coefficient for a grid-type converter. The damping coefficient of the grid-type converter. To match the virtual inertia coefficient of the grid converter, To match the damping coefficient of the grid-type converter, U pu This is the per-unit voltage value. For the active power of the load, k is the synchronization coefficient. p k is the proportionality coefficient. i Here, is the integral coefficient, m is the line impedance synchronization coefficient, and the superscript " "" indicates a small perturbation.

[0048] The transfer function is for a fourth-order system. Under ideal conditions, i.e., without considering the filtering stage, the power frequency response transfer function of the grid-type converter is:

[0049]

[0050] Similarly, the power frequency response transfer function of the grid converter is:

[0051]

[0052] in, To match the output angular frequency of the grid-type converter.

[0053] The transfer function is for a fourth-order system. Under ideal conditions, i.e., without considering the filtering stage, the power frequency response transfer function of the grid converter is:

[0054]

[0055] The power frequency response transfer function (PFRF) of the grid-connected converter and the parallel-connected converter are constructed to achieve consistency, resulting in the constructor. To achieve inertia power matching, i.e., power distribution according to capacity during disturbances, a distribution coefficient K needs to be added before the GFL of the parallel-connected converter. After adjustment, the small-signal PFRF model of the parallel-connected / parallel-connected converter system is as follows: Figure 2 As shown.

[0056] At this point, under ideal conditions, the power frequency response transfer functions of the two types of converters are as follows:

[0057] The power frequency response transfer function of the grid-type converter is adjusted as follows:

[0058]

[0059] The power frequency response transfer function of the grid converter is adjusted to...

[0060] .

[0061] Ideally, the denominators of the power frequency response transfer functions of the two types of converters are the same. To ensure consistency in their power frequency responses, the numerators of the transfer functions must be identical, i.e.:

[0062] make ,

[0063] This ensures that the power frequency response transfer function of the adjusted grid-type converter is consistent in form with that of the ground-type converter.

[0064] At this time, k p k i for:

[0065]

[0066] To achieve inertia-power matching, the active power reference value P also needs to be made... ref The response is a step signal, by Figure 2 It can be seen that, under ideal conditions, the load power P load To the active power reference value P ref The transfer function is:

[0067]

[0068] To make the active power reference value P ref The output is a step signal, i.e., P. load To P ref The transfer function should be:

[0069] ,

[0070] Where n is the capacity ratio of the grid-type converter to the grid-type converter, therefore, the virtual inertia parameter and the primary frequency regulation parameter satisfy:

[0071] .

[0072] Considering K=n+1, we obtain information about k. p and k i Constructor:

[0073] .

[0074] The parameters of the phase-locked loop of the grid converter are configured according to the constructor.

[0075] Figure 4 For an ideal system, the Bode plot of the power frequency response of a grid-connected converter system. Figure 5 Bode plot of power frequency response for a grid-connected converter parallel system under non-ideal conditions. Relevant parameters are shown in Table 1. Among them, GFM-VSG is the virtual synchronous machine control for the grid-connected converter, and GFL-PLL... * The parameter configuration method described in this invention is used for the phase-locked loop control of the grid-connected converter. However, the GFL-PLL, which is used for the phase-locked loop control of the grid-connected converter, does not use the parameter configuration method described in this invention. Figure 4 It can be seen that, under ideal conditions, the parallel system using the parameter configuration method described above can achieve consistency in the power frequency response of the two types of converters, thereby realizing the matching control of inertial power.

[0076] Table 1: Small Signal Model Response Parameters

[0077]

[0078] Depend on Figure 5 It can be seen that, if the filtering stage is considered, the power frequency response of the two types of converters in the system using the parameter configuration method of the present invention has a small difference, while in the parallel system without the parameter configuration method of the present invention, the power frequency response of the two types of converters has a large difference, which proves the effectiveness of the parameter configuration method of the present invention.

[0079] To further verify the effectiveness of the parameter configuration method of this invention, a simulation platform for a parallel system of grid-connected converters was built. Specific parameters are shown in Table 2. The capacity ratio of the two types of converters was set to 2:1. The operating condition was set as a load step disturbance, with an initial load of 2kW and a load step of 2kW. The simulation results are as follows: Figure 6 , Figure 7 As shown, in Figure 6 , Figure 7 In this context, GFM-VSG is the virtual synchronous machine control for grid-type converters, and GFL-PLL... * The parameter configuration method described in this invention is used for the phase-locked loop control of the grid-connected converter. However, the parameter configuration method described in this invention is not used for the phase-locked loop control of the GFL-PLL grid-connected converter.

[0080] Table 2: P / ω Admittance Scan Parameters

[0081]

[0082] Depend on Figure 6 , Figure 7It can be seen that the power frequency response of the two types of converters in the parallel system using the parameter configuration method of the present invention is consistent, and the instantaneous power of the disturbance can be distributed according to the capacity, that is, the inertial power response is matched, which proves the effectiveness of the parameter configuration method of the present invention.

[0083] This invention derives the power frequency response transfer functions of grid-connected and grid-connected converters using a small-signal model of a parallel system of grid-connected and grid-connected converters. Then, based on these power frequency response transfer functions, it derives a phase-locked loop (PLL) parameter configuration method that enables consistent power frequency responses between the two types of converters. This allows for the distribution of instantaneous power during disturbances according to capacity, i.e., inertia power response matching; thus solving the problem of difficulty in matching inertia power in parallel systems of grid-connected and grid-connected converters.

[0084] Example 2

[0085] Based on the parameter configuration method for a grid-connected converter parallel system described in Embodiment 1, this embodiment provides a parameter configuration system for a grid-connected converter parallel system, including a storage medium and a processor; the storage medium is used to store instructions; the processor is used to perform operations according to the instructions to execute the parameter configuration method for a grid-connected converter parallel system described in Embodiment 1.

[0086] Example 3

[0087] Based on the parameter configuration method for a parallel system of grid-connected converters described in Embodiment 1, this embodiment provides an inertia power matching method for a parallel system of grid-connected converters. Using the parameter configuration method for a parallel system of grid-connected converters described in Embodiment 1, phase-locked loop parameters are configured to ensure consistent power and frequency response of the grid-connected converters. This enables the power distribution according to capacity in the parallel system of grid-connected converters during disturbances, i.e., inertia power matching.

[0088] Example 4

[0089] Based on the parameter configuration method for a parallel system of grid-connected converters described in Embodiment 1, this embodiment provides a computer-readable storage medium storing a computer program thereon. When the computer program is executed by a processor, it implements the parameter configuration method for a parallel system of grid-connected converters as described in Embodiment 1.

[0090] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for configuring system parameters of a grid-connected inverter, characterized in that, The method comprises the following steps: Based on the small signal model of the grid-connected converter and grid-following converter, the power frequency response transfer function of the grid-connected converter and the power frequency response transfer function of the grid-following converter are obtained; The power frequency response transfer functions of the grid-connected converter and the grid-following converter are uniformly constructed to obtain a construction function; The phase-locked loop of the grid-following converter is configured according to the construction function; The power frequency response transfer functions of the grid-connected converter and the grid-following converter are uniformly constructed to obtain a construction function, which comprises: a distribution coefficient K is added in front of the grid-following converter to realize power distribution according to capacity when a disturbance occurs; and the power frequency response transfer function of the grid-connected converter is adjusted to, ； The power frequency response transfer function of the grid-following converter is adjusted to, ； where s is a differential operator, k p is a proportional coefficient, k i is an integral coefficient, n is a capacity ratio of grid-forming converter to grid-following converter, is a rated angular frequency of power grid, is a virtual inertia coefficient of grid-forming converter, is a damping coefficient of grid-forming converter, U pu is a voltage per unit, is a synchronization coefficient, where, is a numerator coefficient of transfer function, is a denominator coefficient of transfer function, i = 1, 2, … n, is an output angular frequency of grid-forming converter, is a virtual inertia coefficient of grid-following converter, is a damping coefficient of grid-following converter, is a load active power, m is a line impedance synchronization coefficient, and a superscript ” represents a small perturbation, is an output angular frequency of grid-following converter; Let Thus, the power frequency response transfer function of the adjusted network-forming converter and the power frequency response transfer function of the network-following converter remain consistent in form. The active power reference value P ref is adjusted as a step signal in response; Load power P load The transfer function from the active power reference value P ref to the active power reference value P ； At the same time, let Therefore, the virtual inertia parameter and the first-order frequency modulation parameter satisfy: ; The phase-locked loop filter of the grid-following converter is a first-order inertia element, and the loop filter transfer function is: ； G LP (s) is a first-order inertial element of the phase-locked loop filter; Under the premise of distribution factor K = n + 1 of the grid-connected converter, the construction functions of k p and k i are as follows: 。 2. The method of claim 1, wherein, In an ideal state, the power frequency response transfer function of the grid-connected converter is: 。 3. The method of claim 2, wherein, In an ideal state, the power frequency response transfer function of the grid-following converter is: 。 4. A system for configuring system parameters of a grid-connected inverter parallel operation system, characterized by comprising: The storage medium and the processor are included. The storage medium is used for storing instructions. The processor is used for operating according to the instructions to execute the grid-connected converter and grid-following converter parallel system parameter configuration method in any one of claims 1-3.

5. A method for matching the inertia of a grid-connected inverter system to the power, characterized by The grid-connected converter and grid-following converter parallel system parameter configuration method in any one of claims 1-3 is used for power frequency response consistent phase-locked loop parameter configuration of the grid-connected converter and grid-following converter, which is used for realizing power distribution according to capacity of the grid-connected converter and grid-following converter parallel system at a disturbance moment, i.e. inertia power matching.

6. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the grid-connected converter and grid-following converter parallel system parameter configuration method in any one of claims 1-3.

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